| Birth Date: | 14 February 1904 |
| Birth Place: | New York City, New York, United States |
| Organization: | AMORC |
| Imperator of AMORC | |
| Term: | 1939–1987 |
| Predecessor: | Harvey Spencer Lewis |
| Successor: | Gary L. Stewart |
| Father: | Harvey Spencer Lewis |
Ralph Maxwell Lewis (February 14, 1904 – January 12, 1987), was an American mystic and the second Imperator of the Rosicrucian organisation AMORC from 1939 to 1987. He is the author of a number of books regarding mysticism. His father, Harvey Spencer Lewis, was the first Imperator of AMORC.
Lewis was born to Harvey Spencer Lewis and Mollie Foldsmith Lewis February 14, 1904, in New York City. He received his early education in New York and the New Jersey Military Academy. In 1918, his family took up residence in San Francisco, California, where he began his studies of law and accounting in 1919.
He formally joined AMORC in 1921. His father died in 1939. Following his death, Lewis became the leader (imperator). Lewis was elected.
In Fédération Universelle des Ordres et Sociétés Initiatiques, FUDOSI, he was known by the nomen mysticum (mystical name) "Sar Validivar" and received his initiation in Martinism during the second convention of FUDOSI in September 1936. In the same year, he was initiated as a Rose-Croix Order Kabalistique and in the Traditional Martinist Order in Europe. On August 2, 1939, he was elected by the Board of Directors of the Supreme Grand Lodge of AMORC as Imperator of the order, a position he held until his Great Initiation, on January 12, 1987.
In March 1940, Lewis was elected President of the International Supreme Council of the order Rosæ Crucis. Among the awards he received in his lifetime was the honorary degree of doctor of literature from Andhra University in India, and the star and the cross of science from the International Academic Council.
He founded the Grand Lodge of Brazil, in the summer of 1956, and commissioned new buildings for the Rosicrucian Egyptian Museum in 1966.
Lewis would die January 12, 1987, succeeded by Gary L. Stewart.
On March 28, 1923, he married Gladys Natishna Hammer, who was known to all Rosicrucians as Soror Gladys Lewis.